**6. Effects of digestate on the quality of crops**

Crop yield is very important economical parameter of plant production but nowadays the quality of foods is becoming more and more important. Digestate treatment seems to be very effective to increase the protein content of plants. Banik and Nandi (2004) investigated biogas residual slurry manures (solid digestate) used as supplement with rice straw for preparation of mushroom beds. The application of biomanure increased the protein content of mushroom 38.3-57.0%, while the carbohydrate concentrations were decreased. Results can be seen in Table 10.

Similar results were reported by Makádi et al., (2008b) who found significant increase of protein content of treated soybean. They have found 30.65±1.42% protein in control plants, while these values were 34.83±1.50% and 35.67±1.81% for 5 and 10 L m-2 treatments,

Number of pods Pearson Corr. 0.712\* 0.798\* 0.622 0.850\*\*

Weight of pods Pearson Corr. 0.755\* 0.824\*\* 0.693\* 0.839\*\*

Weight of grain Pearson Corr. 0.742\* 0.832\*\* 0.739\* 0.810\*\*

Thousand seed weight Pearson Corr. 0.695\* 0.690\* 0.827\*\* 0.595

Table 8. Correlations between soil and plant parameters in digestate treatment experiment.

Comparing the effect of digestate and a bacterial manure (Phylazonit MC, the experimental conditions can be found in the section 4.5). The Phylazonit MC treatment increased the green weight of silage maize by 47.18% while the digestate by 142.34%, comparing to the

\* Correlation is significant at the 0.05 level; \*\* Correlation is significant at the 0.01 level.

control. The results obtained can be seen in Table 9 (Makádi et al., 2007).

Treatments Green weight, t ha-1

Table 9. Green weight of silage maize as a second crop after digestate and Phylazonit MC treatment of stubble. (*Data from Makádi et al., 2007*). a, b, c indexes mean the different

The positive effect of Phylazonit MC treatment was the result of its microbes, plant growth promoters and microelement content, while the favourable effect of digestate treatment was caused by its macro- and microelement and high water content and the increase of soluble

Crop yield is very important economical parameter of plant production but nowadays the quality of foods is becoming more and more important. Digestate treatment seems to be very effective to increase the protein content of plants. Banik and Nandi (2004) investigated biogas residual slurry manures (solid digestate) used as supplement with rice straw for preparation of mushroom beds. The application of biomanure increased the protein content of mushroom 38.3-57.0%, while the carbohydrate concentrations were decreased. Results

Similar results were reported by Makádi et al., (2008b) who found significant increase of protein content of treated soybean. They have found 30.65±1.42% protein in control plants, while these values were 34.83±1.50% and 35.67±1.81% for 5 and 10 L m-2 treatments,

Control 6,4482,580a Phylazonit MC 9,4904,081ab Phylazonit MC + digestate 13,9970,493bc Digestate 15,6262,293c

macroelement content of soil because of the increased microbial activity.

statistical groups according to Tukey's test (p<0.05).

**6. Effects of digestate on the quality of crops** 

can be seen in Table 10.

(*Data from Makádi et al., 2008b)*

NO3-N AL-P AL-K AL-Mg

Sig. (2-tailed) 0.031 0.01 0.074 0.004

Sig. (2-tailed) 0.019 0.006 0.039 0.005

Sig. (2-tailed) 0.022 0.005 0.023 0.008

Sig. (2-tailed) 0.038 0.040 0.006 0.091

mean±S.D.

respectively. Changes in amino acid composition of test plants were also very favourable, because almost every essential and non-essential amino acid quantity was increased significantly after digestate treatment. In line with these results the oil content of the treated plants decreased significantly.


Table 10. Effect of supplementation of rice straw with solid digestate on major nutrient contents of mushroom (*Pleurotus sajor caju*). (*Data from Banik and Nandi, 2004*)

Qi et al (2005) examined the effect of fermented waste as organic manure in cucumber and tomato production in North China. Before the vegetables transplantation, the diluted fermented residual dreg was applied 20-30 cm below the soil surface at a rate of 37,500 kg ha-1, while liquid digestate was sprinkled to the soil surface in three vegetables growing stages and on the vegetable leaves once time. They found increasing yield (18.4% and 17.8%) and vitamin C content (16.6% and 21.5%) of treated cucumber and tomato, respectively.

As the results show, the digestate application in solid or liquid form could result significant improvement in the quality of foods without damaging the environment, which is very important for the sustainable environment and healthy life.
